Division by zero and forum skin problem

I have some problem. After upgrading to new version of Web wiz forum, I am experiencing a division by zero error:

Sometimes forum is acting normal and sometimes I get this error.

The problem appears on two pages, forum_topics.asp and forum_posts.asp and it considers this two lines of code:

Forum_topics.asp:

'Count the number of pages for the topics using FIX so that we get the whole number and not any fractions

Forum_posts.asp:

'Count the number of pages for the topics using '\' so that any fraction is omitted

Also.

Sometimes forum skin just disappears leaving forum without any color and without any image. Only text is displayed, whether formatting is absent. That also doesn't happen always. Sometime it happens and sometime everything is ok. When that problem occurs, than also the above described problem (division by zero) is present. So there is something wrong, but I don't know how to fix it and where to search the cause of the problem (in code, maybe in database; I've tried to do something about it but, unfortunately, without any luck.).